Perpendicular.

  • and are orthogonal if
  • If is a subspace of and , is orthogonal to if it is orthogonal to every vector in
  • The set of all vectors orthogonal to a subspace is a itself a subspace, called the Orthogonal Complement of , , W perp

  • is orthogonal to each row of
  • is orthogonal complement to
  • number of columns